1. Field of the Invention
This invention relates to a dry cylinder liner for use in internal combustion engines such as a diesel engine.
2. Description of the Related Art
In diesel engines a dry liner is used in which the liner barrel does not make direct contact with the cooling water. In the most common dry liner, a flange is provided on the upper outer circumference in an axial direction and a grind relief groove is provided below the flange at the outer circumferential surface of the liner barrel. The dry liner is inserted into the cylinder bore of the cylinder block and the flange is fastened along with the gasket, between the lower surface of the cylinder head and the upper surface of the cylinder block by tightening of the head bolts.
However, in recent years demand has steadily mounted for thin-walled dry liners in order to make the engine lighter and more compact. One critical problem that must be dealt with to meet this demand is reduction of tensile stress on the inner circumferential surface of the liner at the grind relief groove below the flange caused by repetitive stress induced by combustion pressure and piston slap during engine operation.
The loose-fit type of the dry liner, which has a gap between the inner circumferential surface of the bore of the cylinder block and the outer circumferential surface of the liner, has the advantage that assembly and maintenance are easy, and no machining of the inner circumferential surface of the liner is needed after assembly. This advantage has caused the loose-fit type liner to see frequent use. During operation of an engine with this type of liner, the liner expands from heat due to a temperature difference between the liner and the cylinder block, so that the outer circumferential surface of the liner barrel makes direct contact with the inner circumferential surface of the bore of the cylinder block. However, this liner also has the disadvantage in that when the liner temperature is low, a gap is present between the liner barrel and the bore of the cylinder block, making the liner barrel prone to deformation.
The tight-fit type of the dry liner has no gap between the outer circumferential surface of the liner and the inner circumferential surface of the bore of the cylinder block and press-fit is carried out during assembly. However in the tight-fit type of the liner, a gap appears just as with the loose-fit type liner when deformation occurs in the cylinder block or the liner in the vicinity of the grind relief groove.
As prior technology for reducing tensile stress on the liner inner circumferential surface at the grind relief groove below the flange, there is for instance a proposal to provide partly press-fit portions below the grind relief groove (see Japanese Utility Model Laid-open No. 6-82466). However changing partly the dimension of the liner barrel is difficult for using conventional centerless grinding.